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. 1993 Aug 15;90(16):7849–7853. doi: 10.1073/pnas.90.16.7849

Two different forms of metarhodopsin II: Schiff base deprotonation precedes proton uptake and signaling state.

S Arnis 1, K P Hofmann 1
PMCID: PMC47240  PMID: 8356093

Abstract

Rhodopsin is a retinal protein and a G-protein-coupled receptor; it shares with both of these families the seven helix structure. To generate the G-interacting helix-loop conformation, generally identified with the 380-nm absorbing metarhodopsin II (MII) photoproduct, the retinal Schiff base bond to the apoprotein must be deprotonated. This occurs as a key event also in the related retinal proteins, sensory rhodopsins, and the proton pump bacteriorhodopsin. In MII, proton uptake from the aqueous phase must be involved as well, since its formation increases the pH of the aqueous medium and is accelerated under acidic conditions. In the native membrane, the pH effect matches MII formation kinetically, suggesting that intramolecular and aqueous protonation changes contribute in concert to the protein transformation. We show here, however, that proton uptake, as indicated by bromocresol purple, and Schiff base deprotonation (380-nm absorption change) show different kinetics when the protein is solubilized in suitable detergents. Our data are consistent with a two-step reaction:

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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